From: Tom Lane <tgl@sss.pgh.pa.us>
To: exclusion@gmail.com
cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #16814: Invalid memory access on regexp_match with .* and BRE
In-reply-to: <16814-6c5e3edd2bdf0d50@postgresql.org>
References: <16814-6c5e3edd2bdf0d50@postgresql.org>
Comments: In-reply-to PG Bug reporting form <noreply@postgresql.org>
	message dated "Thu, 07 Jan 2021 19:00:01 +0000"
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Content-ID: <323715.1610126386.1@sss.pgh.pa.us>
Date: Fri, 08 Jan 2021 12:19:46 -0500
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PG Bug reporting form <noreply@postgresql.org> writes:
> When executing the following regexp call:
> select regexp_match('abc', '.*', 'b');
> valgrind detects an error:

Hah, nice one.  It gives the wrong answer too, at least it does most of
the time for me:

# select regexp_match('abc', '.*', 'b');
 regexp_match 
--------------
 {""}
(1 row)

That's because it's acting like the pattern is '.*?' (prefer shortest
match) rather than '.*'.

This bug is well over the age of consent, btw.  Tcl's got it too,
so it surely is aboriginal in Henry Spencer's code.

Thanks for the report!

			regards, tom lane